+
+bool
+is_not_escape_character (Byte c)
+{
+ switch (c)
+ {
+ case '-':
+ case '.':
+ case '/':
+ case '0'...'9':
+ case ':':
+ case 'A'...'Z':
+ case '_':
+ case 'a'...'z':
+ return true;
+ }
+
+ return false;
+}
+
+LY_DEFINE (ly_string_percent_encode, "ly:string-percent-encode",
+ 1, 0, 0, (SCM str),
+ "Encode all characters in string @var{str} with hexadecimal"
+ " percent escape sequences, with the following exceptions:"
+ " characters @code{-}, @code{.}, @code{/}, and @code{_}; and"
+ " characters in ranges @code{0-9}, @code{A-Z}, and @code{a-z}.")
+{
+ LY_ASSERT_TYPE (scm_is_string, str, 1);
+
+ string orig_str = ly_scm2string (str);
+ string new_str = "";
+
+ vsize i = 0;
+ vsize n = orig_str.size ();
+
+ while (i < n)
+ {
+ Byte cur = orig_str[i];
+
+ if (is_not_escape_character (cur))
+ new_str += cur;
+ else
+ {
+ new_str += '%';
+ new_str += String_convert::bin2hex (cur);
+ }
+
+ i++;
+ }
+
+ return ly_string2scm (new_str);
+}
+